High-field superconductors

Abstract

A method of increasing the upper critical field of a crystalline superconducting material is provided, which comprises the steps of converting the crystalline superconducting material to a substantially amorphous state, and then re compacting and crystallising the material. The method also has the effect of increasing the critical current density of the material, and is effective with both brittle and ductile superconductors.

1 . A method of increasing an upper critical field of a crystalline superconducting material, comprising the steps of: 
 converting the crystalline superconducting material to a substantially amorphous state material; and    re-compacting the substantially amorphous state material.    
     
     
         2 . The method of  claim 1 , further comprising the step of crystallizing the substantially amorphous state material.  
     
     
         3 . The method of  claim 1 , wherein a critical current density (J C ) of the crystalline superconducting material is increased.  
     
     
         4 . The method of  claim 2 , wherein the step of crystallizing the substantially amorphous state material comprises nanocrystallization of the material.  
     
     
         5 . The method of  claim 1 , wherein the step of converting the crystalline superconducting material to the substantially amorphous state material comprises pumping energy into the material to increase its energy state from a low level crystalline state to a high level amorphous state.  
     
     
         6 . The method of  claim 5 , wherein the increase in energy state further comprises a mechanical attrition step.  
     
     
         7 . The method of  claim 6 , wherein the mechanical attrition step comprises ball-milling.  
     
     
         8 . The method of  claim 1 , wherein the step of re-compacting the substantially amorphous state material further comprises the step of applying at least one of heat or pressure.  
     
     
         9 . The method of  claim 2 , wherein the step of crystallizing the substantially amorphous state material further comprises the step of applying at least one of heat or pressure.  
     
     
         10 . The method of  claim 8 , wherein the step of applying at least one of heat or pressure comprises thermomechanical processing.  
     
     
         11 . The method of  claim 10 , wherein the thermomechanical processing comprises at least one of hot isostatic pressing (HIP) or annealing.  
     
     
         12 . The method of  claim 1 , wherein the crystalline superconducting material is a brittle superconductor.  
     
     
         13 . The method of  claim 12 , wherein the brittle superconductor is Nb 3 Sn.  
     
     
         14 . The method of  claim 1 , wherein the crystalline superconducting material is a ductile superconductor.  
     
     
         15 . The method of  claim 14 , wherein the ductile superconductor is doped NbTi.  
     
     
         16 . The method of  claim 1 , wherein the crystalline superconducting material is an elemental superconductor or an alloy thereof.  
     
     
         17 . The method of  claim 2 , wherein the step of crystallizing the substantially amorphous state material further comprises controlling the crystallization kinetics of an amorphous solid by optimizing heat treatment conditions for the amorphous phase to crystallize into a polycrystalline material with ultrafine crystallites.  
     
     
         18 . The method of  claim 17 , wherein a crystallite nucleation rate is high and a crystallite growth rate is small.  
     
     
         19 . The method of any of  claim 5 , wherein the step of re-compacting the substantially amorphous state material further comprises applying at least one of heat or pressure, wherein parameters for applying at least one of heat or pressure and pumping energy into the substantially amorphous state material are selected for the crystalline superconducting material to which the method is to be applied.  
     
     
         20 . A crystalline superconducting material treated according to the method of  claim 1 .  
     
     
         21 . A crystalline superconducting material as claimed in  claim 19 , having very small grain size, with many scattering centers and pinning defects inside the grains.  
     
     
         22 . The method of  claim 9 , wherein the step of applying at least one of heat or pressure comprises thermomechanical processing.  
     
     
         23 . The method of  claim 5 , further comprising the step of crystallizing the substantially amorphous state material by applying at least one of heat or pressure, wherein parameters for applying at least one of heat or pressure and pumping energy into the substantially amorphous state material are selected for the crystalline superconducting material to which the method is to be applied.